Artificial light regulation is used in lighting systems. The aim of artificial light regulation is to achieve a setpoint illuminance consistently even under a changing extraneous light influence. By way of example, the illuminance on a reference surface, for example a work surface in an office, is meant to be kept as constant as possible even under variable and unknown extraneous light influence. To this end, a regulator that is provided with the present illuminance by at least one light sensor and artificial lighting that the regulator can use to compensate for a change in the illuminance within the limits of the artificial lighting are set. Such artificial light regulation can be used in light control systems that are used for interior lighting, for example.
Conventional artificial light regulating systems may be embodied such that they change their actuating element by the smallest possible unit in each control step in response to a discrepancy between an actual value and a setpoint value for an illuminance sensed by a sensor. Such an approach usually results in a slow approach to the setpoint value in multiple steps. If the difference between the actual value and the setpoint value is large in comparison with the increment of the actuating element that is used in each control step, the period of time before the setpoint value is reached again can likewise become large. If, by contrast, the increment is chosen to be large in order to achieve a faster approach to the setpoint value, there is the danger of “overshoot”, in which a range of acceptable illuminances is missed and further actuation commands are required for compensation. Such overshoot can result in undesirable fluctuations in the illuminance. Both in the case of excessively small and in the case of excessively large actuation steps, the outlined scenarios can result in a large number of actuation commands needing to be produced. This can lead to an undesirable level of utilization of the available computation power and/or of transmission bandwidths for actuation commands. By way of example, the latter is a problem when the actuation commands are transmitted as digital commands via a bus, for example a DALI bus.
Furthermore, both excessively slow adjustment of the illuminance and an excessively fast change, particularly an “overshoot”, are perceived as annoying.
Regulating systems in which the size of the control step is determined on the basis of the difference between the actual value and the setpoint value using one or more firm parameters, or parameters firmly set when the regulator is initialized, are also known. Such regulators also reach the setpoint value only after a series of control steps, which in turn can result in slow adjustment to suit the setpoint value or in “overshoot”.
WO 02/45478 A1 describes information systems in which an illuminance is adjusted on the basis of the extraneous light. In this case, an increment or an actuation step is stipulated on the basis of the difference between the actual value and the setpoint value. The increment chosen for a subsequent control step is dependent only on the actual value of the illuminance that is determined following the preceding control step. The possible increments have fixed values. This can lead to difficulties if, by way of example, the behavior of a luminaire changes on account of aging. Adjustments to suit different luminaires can be involved in terms of work and cost, since appropriate maintenance may be required in situ.
It is an object of the invention to provide a method and an apparatus for regulating an artificial light control that reduce the risk of creep or overshoot behavior. It is an object of the invention to provide such methods and apparatuses as facilitate the adjustments to suit different luminaires or to suit different luminous fluxes, for example, with increasing aging of luminaires without this requiring separate maintenance to be performed on the regulator.